Conventional chip manufacturing methods initially thin a sheet-like object to be processed made of silicon by polishing it to a desirable thickness required and subsequently form functional devices on one main face of the thinned object. Then, as illustrated in Patent Literature 1, for example, a laser light is converged at the object, so as to form a modified region within the object, and thereafter an external stress is applied to the object. This can cut the object into individual pieces from the modified region acting as a start point, whereby chips are obtained.